Carbon nanotubes (CNTs) are much stronger than steel and show remarkable electrical and mechanical properties such as metallic and semiconducting behavior.
Doping of elements such as nitrogen and boron into CNTs has been shown to activate their surfaces and add additional electronic states around the Fermi level. Nitrogen-doped (N-doped) CNTs have been suggested as promising materials for applications in field emission, energy conversion, energy storage, and other applications [1]. Nitrogen-doped carbon structures such as nanotubes, graphene, and particles have been reported to show high oxygen reduction reaction (ORR) activity in alkaline media [2-8]. These reports suggest that such structures may have applications, for example, in cathodes of alkaline fuel cells, metal-air batteries, and chlor-alkali electrolysis. N-doped CNTs have been reported to have an oxygen reduction reaction activity comparable to that of a Pt/C catalyst [2], are under study for use in Li-storage and gas sensors. Toxicological studies of N-doped CNTs in rats showed significantly lower toxic response than for their undoped counter parts [9], which suggests a higher biocompatibility when they are doped compared to when they are not.
N-doped CNTs have been synthesized by classical CVD, aerosol assisted CVD, and post-treatment of pristine CNTs with ammonia gas [2]. These methods require multiple steps to dope nitrogen into the CNTs, which may limit their mass production.
There remains a need for inexpensive, simpler methods for preparing N-doped carbon tubes.